Rapid warmup furnace for processing electron discharge device cathodes

ABSTRACT

The disclosed furnace comprises two spaced apart vertical heat runs for processing electron discharge device cathodes carried by thin strip material. Each of the vertical heat runs comprises a heating coil through which the strip material passes. The heating coils are surrounded by tubular jackets such as copper sleeves which are water cooled. At the uppermost portion of the heat runs a water cooled pulley is provided for the strip. Controlled atmospheres can be provided within the heat runs. While the invention is not so limited it is particularly applicable to the processing of cathode ray tube cathodes which comprise a cathode sleeve which is generally circular and hollow and which is closed at one end by a cathode cap. It is generally the cathode cap which is attached to and carried by the strip. The material is generally nickel or a nickel alloy.

United States Patent 1191 Kerstetter et al.

RAPID WARMUP FURNACE FOR PROCESSING ELECTRON DISCHARGE mzvrcn CATHODES Inventors: Donald R. Kerste tter; John J. Regec,

. both of Emporium, Pa.

Assignee: GTE S'ylvania Incorporated, Seneca Falls, N,Y.

Filed: Au .22, 1973 Appl. No.: 390,615

References Cited UNITED STATES PATENTS Rudolph et a1. 219/214 5] Apr. 16, 1974 3,045,097 7/1962 Sellers 219/552 X' 3,143,167

- Primary ExaminerVolodymyr Y. Mayewsky- [57 ABSTRACT The disclosed furnace comprises two spaced apart vertical heat runs for processing electron'discharge de vice cathodes carried by thin strip material. Each of the vertical heat runs comprises a heating coil through which the strip material passes. The heating coils are surrounded by tubular jackets such as copper sleeves which are water cooled. At .the uppermost portion of the heat runs a water cooled pulley is provided for the strip, Controlled atmospheres can be provided: within the heat runs.

While the invention is not so limited it is particularly applicable to the processingv of cathode ray tube cathodes which comprise a cathode. sleeve which is generally circular and hollow and which is closed at one end by a cathode cap. it is generally the cathode cap which is attached to and carried by the strip. Th material is generally nickel or a nickel alloy;

5 Claims, 6 Drawing Figures 8/1964 Vieth 165/64 X".

PATENTEDAPR 16 I974 SHEEI 1 0F 3 PATENTEMPR 16 I91 13,80,158

SHEET 3 [IF 3 RAPID WARMUP FURNACE FOR PROCESSING ELECTRON DISCHARGE DEVICE CATI -IODES BACKGROUND OF THE INVENTION completed cathodes which have existed as individual units. These units were generally placed in trays of one form or another and then inserted into the various oxidizing and reducing atmospheres for firing. This procedure has been most costly and time consuming. Furtherinore, the furnaces have been slow to reach proper temperatures and the processing time has been long. Also, a large mass of cathodes are processed at one time which limits the cleaning effect on each cathode and places definite limits on firing times and temperatures.

It would be a distinct advance in the art if a meansof I faster processing of cathodes could be accomplished, particularly one wherein the cathodes are separated from each other without time-temperature limitations.

OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, an object of this invention to obviate the disadvantages of the prior art.

It is a further object of the invention to include furnace means which can be included in an automated cathode assembly line.

' ltis a furtherobject of this invention to produce a furnace for processing electron discharge device cathodes which rapidly reaches the necessary operating temperatures while maintaining a cool wall, and which cools down quickly in the event the machine must be shut down and not over process the in process" prod- LlCt. l t

It is still a further object of this invention to provide such a furnace which is capable of acting upon continuous cathode strip material which .is passing therethrough.

These objects are accomplished in one aspect of the invention by the provision of a furnace having an extremely rapid warmup time which comprises two spaced apart vertical runs. Each of these vertical runs comprises a heating coil contained within tubular sleeve of suitable, heat conducting material, such as copper. Cooling means are positioned in operative relationship to the tubular jackets. Cathode material enters the furnace at the base of one of the vertical heat runs and rises upwardly therethrough within the hollow space provided by the heating coil. As it exits from the uppermost portion of the first heat run it passes over a water cooled pulley and then descends through the coil of the second heat run and exits from the bottom thereof. The furnace has the capability of being proabout 1, l00 C. In operation, the furnace reaches operating temperature in approximately 20 seconds from turn-on and can be cooled to room temperature after shut-off in less than 1 minute.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a perspective view of a cathode ray tube cathode which can be processed utilizing the furnace of this invention;

FIG. 2 is a perspective view of the cathode of FIG. I mounted in a processing strip;

FIG. 3 is an elevational view of the furnace assembly;

FIG. 4 is an elevational sectional view showing the working components of the furnace;

FIG. 5 is a sectional plan view of the upper section of the furnace taken along the line 55 of FIG. 4; and

FIG. 6 is a sectional view of the heat runs taken along the line 6-6 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in conjunction with the above-described drawings.

Referring now to the invention with greater particularity, there is shown in FIG. 1 a cathode assembly 10 which is comprised of a hollow cathode sleeve 12 having one end thereof closed by a cathode cap 14. Such cathodes are usedin color cathode ray tubes. Cathodes 10 are generally formed as a two piece unit. The sleeve 12 can be formed by conventional tube forming tech- I niques and the cathode cap can be die drawn'from a thin strip of material. In FIG. 2 is shown an example of such a strip having the formed cathode caps 14 still attached to a strip 16 as by web 17. The cathode sleeve 12 has already been inserted under pressure into the cathode cap 14 and is thereby carried along with move- I ment of the strip 16.

The processing furnace of the invention is shown in an overall elevational view in FIGJ3. Herein furnace 20 is provided'with a covering hood 22. The hood 22 is provided on two sides with a plurality of cars 24 which are apertured and engage hood guides 26. These ears and guides allow the hood 22 to be raised for visual inspection of the furnace components. To aid in raising the hood it is counterbalanced as by a counter weight 28 attached to one end of a line 30 which has its other end attached to the upper portion of the hood- 22. Viewing ports 32can also be provided in a front surface of hood 22. The phantom line16 corresponds to the cathode strip 16 and indicates the direction of travel of the strip through the furnace.

As can be seen in FIG. 4, the furnace itself comprises first and second heating units 34 and 36 respectively which are vertically arrayed. The heating units comprise a helical electrical heating coil 40 which is supported within a tubular jacket 41 by means of four spaced ceramic support rods 42, 43, 44, and 45. Each of these rods has staggered widened projections 46 thereon for engaging various turns of the coil 40 and supporting the same. Surrounding the tubular jacket, which is preferably of copper are cooling means 48.

Means 48, in this instance, comprises a double helix of hollow copper tubing which is brazed to the jacket 41. Inlet means 50 andan outlet means 52 are provided for the ingress and egress of a cooling medium, such as water.

The heating coils 40 can be two separate units or they can be electrically connected together as by a heating coil continuation 54. Again, the phantom line 16 corresponds to the cathode strip and indicates the direction of travel. It will be seen that the strip goes up the first heating unit or heat run 34 and after it exits therefrom passes over a pulley 58 which can be more clearly seen in FIG. 5. Pulley 58 is journaled in a bushing 60 and the entire unit is water cooled as by water cooling coils 62 and 64. The water cooling coils can be supported by brackets 66 and 68.

A furnace of this design can be utilized either for oxidation or for reduction. It is primarily useful as a reducing furnace wherein a hydrogen atmosphere is pumped therethrough. When so employed, the heating unit should be tungsten and the water cooling means should be of the double helix variety. When employed as an oxidizing furnace, the heating coil can be nichrome or any suitable resistance heating alloy and only a single helix of water cooling tubing is required, since the temperature need only approach 900 C. This furnace construction, utilizing the vertical heat runsfor the mate.-

rial being processed, is extremely efficient when the material is relatively thin, that is, of the order of 4 to 7/l0O0s of an inch thick. When the heating units are tungsten coils the coils themselves should be capable of achieving a temperature of l,600. The tubular jackets 41 are about 2 /2 inches in diameter and the water cooling tubes which are brazed thereto are also copper. A high volume of water pumped through the tubing gives in effect a cool wall furnace. The excellent heat conductivity of the copper and the water cooling maintains the outer wall temperature of the copper sleeve at about 120 F, while, as mentioned above, the coil temperature can reach l,600 C. The material being processed goes up the first heat run 34 and passes over the freely rotating pulley 58. Again,as mentioned above, the entire wheel or pulley 58 is maintained in a cooled area of the furnace by means of the water cooling coils 62 and 64. Thus, the material being processed is cooled briefly in the period of time during which it leaves the first heat run 34'and before it enters the second heat run 36. I

When hydrogen is being pumped through both runs of the furnace to maintain a reducing atmosphere, it is preferable that before the hydrogen is exited at the bottom of the runs it be mixed with about percent nitrogen to reduce any possibility of the formation of an explosive atmosphere. The main feature of this type of furnace is that it can be raised to operating temperature from room temperature .in about 20 seconds. Likewise,

in the event of a stoppage of the cathode strip 16 being fed therethrough, the furnace can be cooled in about 30 seconds by merely inactivating the tungsten coils. When the furnace is being utilized to process cathode strip, the strip will be in the firing zone of the furnace for about three minutes.

While there have been shown what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

l. A rapid warmup, vertical run furnace for processing electron discharge device cathodes, said furnace comprising: two spaced apart, structurally united vertical heating units each comprising a elastic heating coil of sufficient internal diameter to allow a continuous strip of said cathodes to pass therethrough; a plurality of electrically insulating posts positioned about the outer diameter of each of said coils to aid in supporting said coil; a tubular jacket'spaced from but surrounding each of said coils and said posts, a pulley mounted above said heating units for passing over said continuous strip, cooling means affixed to said pulley and each of said tubular jackets, and a removable hood covering said heating units and said pulley.

2. The furnace of claim 1 wherein said heating coils are tungsten.

3. The furnace of claim 1 wherein said jackets are copper.

4. The furnace of claim 1 wherein said cooling means comprises at least one helix of copper tube about each of said jackets, said tubing being formed to accommodate the passage of a cooling fluid.

' 5. The furnace of claim 4 wherein said cooling means comprises a double helix of copper tube which is brazed to said jacket.

' Patent: No. 3,8 U4 158 Date 'f 19M Inventqrqfg) Dbnalci R.'KETEEGE*;EI and John J. Re'gec it is; tertifi-ed that arm: appears in the aboveddentified patent zm "that aafile'tters Patam: am hereby co'z'zectefi as sl'aown beiww:

Column 4, line 25 pleasa cleiete a elastic heating anci insert therefor an e'ie 'ctrilc heating Signed and sealed this lO'th clay of September 197 (SEALI; Attes c-fi MCCOY Ma GIBSON, JR. Ca MARSHALL DANN Attes'tingofficer Commissioner of Patents I Pawn: No. ,3 304 153 Inventoris) v R,'Ke': :ett and John J Regec It is: tertified that error appears in a'bove-ifiencified patent and that said Ltters' Patent hereby co'zrectad as snow beiaw:

Column line 25 P l te a elastic heating" and insert therein: an e'iettric heating Signed and sealed this lO't'n day of September 337A.

(SEAL) McCOY l h GIBSON, JR. C. MARSHALL DANN Attes'ting Officer Commissioner of Patents 

1. A rapid warmup, vertical run furnace for processing electron discharge device cathodes, said furnace comprising: two spaced apart, structurally united vertical heating units each comprising a elastic heating coil of sufficient internal diameter to allow a continuous strip of said cathodeS to pass therethrough; a plurality of electrically insulating posts positioned about the outer diameter of each of said coils to aid in supporting said coil; a tubular jacket spaced from but surrounding each of said coils and said posts, a pulley mounted above said heating units for passing over said continuous strip, cooling means affixed to said pulley and each of said tubular jackets, and a removable hood covering said heating units and said pulley.
 2. The furnace of claim 1 wherein said heating coils are tungsten.
 3. The furnace of claim 1 wherein said jackets are copper.
 4. The furnace of claim 1 wherein said cooling means comprises at least one helix of copper tube about each of said jackets, said tubing being formed to accommodate the passage of a cooling fluid.
 5. The furnace of claim 4 wherein said cooling means comprises a double helix of copper tube which is brazed to said jacket. 